One of the methods employed in manufacturing pipe insulation from fibrous mineral material, such as glass wool comprised of glass fibers, is to manufacture a flat pelt of glass wool containing a binder, fold the glass wool into a cylindrical shape, and advance the glass wool through the mold while passing hot curing gases therethrough to cure the binder. Typically, the glass wool is folded around a center mandrel, and this mandrel can be perforated for the passage of hot curing gases from the mandrel into the inside diameter of the pipe insulation. Also, the cylindrical curing mold is typically surrounded by one or more zones of hot curing gases, and the curing mold usually has openings for the passage of curing gases from these zones into the glass wool. The process can be run rather continuously, producing a substantially rigid insulation product.
One of the problems associated with the continuous insulation manufacturing processes of the prior art is that the binder, coming in contact with the hot mold, tends to cure and build up a residue of binder and glass fibers on the surfaces of the mold. A typical binder suitable for use in pipe insulation is a phenol formaldehyde urea binder, which requires temperatures of 400.degree. F. or greater for curing in the mold. In particular, the binder and fibers collect in the openings in the mold which provide communication between the glass wool and the hot gas supply and exhaust zones. Under normal operating conditions, these curing molds require shutdown and substantial disassembly for cleaning of fiber and binder residue from the holes in the mold wall, thereby greatly reducing the efficiency of the machines. The frequency of these required cleanings is usually in the range of from about 1 to about 4 hours. There is a need for a method and apparatus for cleaning pipe insulation molds without interrupting the continuous molding process.